Hi Lima.
I think what you need is to change the Sale price automatically when you do purchase order..
In Sales Module, enable advanced PriceLists and configure the price list based on Cost. (https://m.youtube.com/watch?v=KFe3xKQO_MA)
In the Inventory Module product categories, choose Costing or Valuation Method between Automatic or Average Costing. (https://m.youtube.com/watch?v=clog3lmVMno)
When the purchase order is done.. It will affect your sales Price depending on how you have set the costing method.. (although not ideal if there significant changes in purchase prices)
On the other hand, if you want to have price list based on vendor price, you may need to custom module to achieve it.
**hope this is what you wanted.**